In New York City, high levels of HIV infection among intravenous drug users (IVDU) and relatively high levels of HIV transmission from IVDU to heterosexual partners mandate efforts to reduce the risk of infection by or transmission from IVDUs, their sex partners, and prostitutes who associate with IVDUs. Studies show that such efforts should concentrate not only upon education but also social support for lasting protective behavioral change. The proposed project includes 3 components aimed at the target populations with the goal of decreasing behaviors that risk infection by or transmission of HIV: (1) Ex-addict outreach workers who educate IVDU and others about AIDS, offer to transport them to alternative site antibody testing centers, and make drug treatment referrals. (2) Formal self-help groups that educate about AIDS while helping participants come to terms with it emotionally; provide social support for risk and transmission reduction, access to antibody testing, and referrals for drug or other treatment; and train participants to conduct emotionally supportive outreach education to friends. (3) Informal self-help groups conducted with naturally-occurring friendship groups in normal social settings or in a convenient meeting space. These aim to get people who inject drugs together, or who influence each other's sexual practices, to support each others' protective efforts, and to develop collective perspectives, norms, and rituals that facilitate risk reduction. Transportation to alternative site testing centers and drug treatment referrals will be provided. In all 3 outreach projects, participants will be encouraged to use the knowledge and social skills they acquire to reach out to others who are at risk. To guide project efforts and to help us understand reactions by the target populations, a small street ethnography will be conducted. Process evaluation will provide information about what is actually happening in the project so it can be improved and outcomes can be more fully understood. Data will be collected for the national evaluation and, if necessary, supplemented to allow particularly important analyses. Evaluation will study changes in knowledge, attempted risk reduction, achieved risk reduction, and participants' attempts to help their friends and networks reduce their risks. Analysis will determine the magnitude and determinants of these outcomes as well as the effects of knowledge and social support upon attempted behavioral change, achieved behavioral change, and participants' outreach efforts.